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Detectability of Discrete Event Systems
"... In this paper, we investigate the detectability problem in discrete event systems. We assume that we do not know initially which state the system is in. The problem is to determine the current and subsequent states of the system based on a sequence of observation. The observation includes partial ev ..."
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Cited by 628 (12 self)
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In this paper, we investigate the detectability problem in discrete event systems. We assume that we do not know initially which state the system is in. The problem is to determine the current and subsequent states of the system based on a sequence of observation. The observation includes partial event observation and/or partial state observation, which leads to four possible cases. We further define four types of detectabilities: strong detectability, (weak) detectability, strong periodic detectability, and (weak) periodic detectability. We derive necessary and sufficient conditions for these detectabilities. These conditions can be checked by constructing an observer, which models the estimation of states under different observations. The theory developed in this paper can be used in feedback control and diagnosis. If the system is detectable, then the observer can be used as a diagnoser to diagnose the failure states of the system.
Games for synthesis of controllers with partial observation
 Theoretical Computer Science
"... The synthesis of controllers for discrete event systems, as introduced by Ramadge and Wonham, amounts to computing winning strategies in parity games. We show that in this framework it is possible to extend the specifications of the supervised systems as well as the constraints on the controllers ..."
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Cited by 82 (10 self)
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The synthesis of controllers for discrete event systems, as introduced by Ramadge and Wonham, amounts to computing winning strategies in parity games. We show that in this framework it is possible to extend the specifications of the supervised systems as well as the constraints on the controllers by expressing them in the modal µcalculus. In order to express unobservability constraints, we propose an extension of the modal µcalculus in which one can specify whether an edge of a graph is a loop. This extended µcalculus still has the interesting properties of the classical one. In particular it is equivalent to automata with loop testing. The problems such as emptiness testing and elimination of alternation are solvable for such automata. The method proposed in this paper to solve a control problem consists in transforming this problem into a problem of satisfiability of a µcalculus formula so that the set of models of this formula is exactly the set of controllers that solve the problem. This transformation relies on a simple construction of the quotient of automata with loop testing by a deterministic transition system. This is enough to deal with centralized control problems. The solution of decentralized control problems uses a more involved construction of the quotient of two automata. This work extends the framework of Ramadge and Wonham in two directions. We consider infinite behaviours and arbitrary regular specifications, while the standard framework deals only with specifications on the set of finite paths of processes. We also allow dynamic changes of the set of observable and controllable events. 1
Diagnosis of Asynchronous Discrete Event Systems, a Net Unfolding Approach
 IEEE TRANS. ON AUTOMATIC CONTROL
, 2001
"... In this paper we formulate asynchronous diagnosis by means of hidden state history reconstruction, from alarm observations. We follow a socalled true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order ..."
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Cited by 69 (28 self)
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In this paper we formulate asynchronous diagnosis by means of hidden state history reconstruction, from alarm observations. We follow a socalled true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order model of time, in which local events are ordered if they are either generated on the same site, or related via some causality relation. Our basic mathematical tool is that of net unfoldings originating from the Petri net research area. This study was motivated by the problem of event correlation in telecommunications network management.
An Operating Guideline Approach to the SOA
 ANNALS OF MATHEMATICS, COMPUTING & TELEINFORMATICS
, 2005
"... Interorganizational cooperation is more and more organized by the paradigm of services. The serviceoriented architecture (SOA) provides a general framework for service interaction. It describes three roles, service provider, service requester, and service broker, together with the three operations ..."
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Cited by 62 (13 self)
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Interorganizational cooperation is more and more organized by the paradigm of services. The serviceoriented architecture (SOA) provides a general framework for service interaction. It describes three roles, service provider, service requester, and service broker, together with the three operations publish, find, and bind. We provide
A General Architecture for Decentralized Supervisory Control of DiscreteEvent Systems
 ACCEPTED FOR PUBLICATION IN DISCRETE EVENT DYNAMIC SYSTEMS: THEORY AND APPLICATIONS
, 2002
"... We consider a generalized form of the conventional decentralized control architecture for discreteevent systems where the control actions of a set of supervisors can be "fused" using both union and intersection of enabled events. Namely, the supervisors agree a priori on choosing "fu ..."
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Cited by 45 (5 self)
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We consider a generalized form of the conventional decentralized control architecture for discreteevent systems where the control actions of a set of supervisors can be "fused" using both union and intersection of enabled events. Namely, the supervisors agree a priori on choosing "fusion by union" for certain controllable events and "fusion by intersection" for certain other controllable events. We show that under this architecture, a larger class of languages can be achieved than before since a relaxed version of the notion of coobservability appears in the necessary and sufficient conditions for the existence of supervisors. The computational complexity ofverifying these new conditions is studied. A method of partitioning the controllable events between "fusion by union" and "fusion by intersection" is presented. The algebraic properties of coobservability in the context of this architecture are presented. We show that appropriate combinations of fusion rules with corresponding decoupled local decision rules guarantee the safety of the closedloop behavior with respect to a given specification that is not coobservable. We characterize an "optimal" combination of fusion rules among those combinations guaranteeing the safety of the closedloop behavior. In addition, a simple supervisor synthesis technique generating the in mal prefixclosed controllable and coobservable superlanguage is presented.
PolynomialTime Verification of Diagnosability of PartiallyObserved DiscreteEvent Systems
 ACCEPTED FOR PUBLICATION IN TRANSACTIONS OF AUTOMATIC CONTROL
, 2002
"... The problem of verifying the properties of diagnosability and Idiagnosability is considered. We present new polynomialtime algorithms for deciding diagnosability and Idiagnosability. These algorithms are based on the construction of a nondeterministic automaton called a verifier. ..."
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Cited by 44 (4 self)
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The problem of verifying the properties of diagnosability and Idiagnosability is considered. We present new polynomialtime algorithms for deciding diagnosability and Idiagnosability. These algorithms are based on the construction of a nondeterministic automaton called a verifier.
Undecidable Problems of Decentralized Observation and Control
, 2001
"... We introduce a new notion of decentralized observability for discreteevent systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based on thi ..."
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Cited by 40 (3 self)
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We introduce a new notion of decentralized observability for discreteevent systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based on this result, we show that a related decentralized control problem is also undecidable. We finally provide an extensive study relating our work to existing work in the literature.
Distributed monitoring of concurrent and asynchronous systems
, 2005
"... In this paper we study the diagnosis of distributed asynchronous systems with concurrency. Diagnosis is performed by a peertopeer distributed architecture of supervisors. Our approach relies on Petri net unfoldings and event structures, as means to manipulate trajectories of systems with concurre ..."
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Cited by 35 (16 self)
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In this paper we study the diagnosis of distributed asynchronous systems with concurrency. Diagnosis is performed by a peertopeer distributed architecture of supervisors. Our approach relies on Petri net unfoldings and event structures, as means to manipulate trajectories of systems with concurrency. This article is an extended version of the paper with same title, which appeared as a plenary address in the Proceedings of CONCUR’2003.
Markov Nets: Probabilistic Models for distributed and concurrent systems
 IEEE Transactions on Automatic Control
, 2001
"... For distributed systems, i.e. large networked complex systems, there is a drastic difference between a local view and knowledge of the system, and its global view. Distributed systems have local state and time, but do not possess global state and time in the usual sense. In this paper, motivated by ..."
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Cited by 33 (16 self)
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For distributed systems, i.e. large networked complex systems, there is a drastic difference between a local view and knowledge of the system, and its global view. Distributed systems have local state and time, but do not possess global state and time in the usual sense. In this paper, motivated by the monitoring of distributed systems and in particular of telecommunications networks, we develop Markov nets as an extension of Markov chains and hidden Markov models (Hmm) for distributed and concurrent systems. By a concurrent system, we mean a system in which components may evolve independently, with sparse synchronizations. We follow a socalled true concurrency approach, in which neither global state nor global linear time are available. Instead, we use only local states in combination with a partial order model of time. Our basic mathematical tool is that of Petri net unfoldings. Keywords : discrete event systems, stochastic Petri nets, unfoldings. 1 Motivations Distributed network...
Gadara: Dynamic Deadlock Avoidance for Multithreaded Programs
"... Deadlock is an increasingly pressing concern as the multicore revolution forces parallel programming upon the average programmer. Existing approaches to deadlock impose onerous burdens on developers, entail high runtime performance overheads, or offer no help for unmodified legacy code. Gadara autom ..."
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Cited by 31 (8 self)
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Deadlock is an increasingly pressing concern as the multicore revolution forces parallel programming upon the average programmer. Existing approaches to deadlock impose onerous burdens on developers, entail high runtime performance overheads, or offer no help for unmodified legacy code. Gadara automates dynamic deadlock avoidance for conventional multithreaded programs. It employs wholeprogram static analysis to model programs, and Discrete Control Theory to synthesize lightweight, decentralized, highly concurrent logic that controls them at runtime. Gadara is safe, and can be applied to legacy code with modest programmer effort. Gadara is efficient because it performs expensive deadlockavoidance computations offline rather than online. We have implemented Gadara for C/Pthreads programs. In benchmark tests, Gadara successfully avoids injected deadlock faults, imposes negligible to modest performance overheads (at most 18%), and outperforms a software transactional memory system. Tests on a real application show that Gadara identifies and avoids both previously known and unknown deadlocks while adding performance overheads ranging from negligible to 10%. 1